Technical Field
The present invention relates to a control device for controlling a transmission torque capacity of a starting clutch interposed in a torque transmission path to transmit a rotation of a power or driving source such as an engine to wheels during shift by an automatic transmission which is not limited to an automated manual transmission AMT which automates a manual transmission, a stepped automatic transmission of planetary gear type, but also includes a V-belt type continuously variable transmission or a toroidal-type continuously variable transmission.
Related Art
It is usual to configure the automatic transmission such that the wheels are kept in a stopped state or in a creeping or low speed state with the driving source in operation by restricting the power from the power source to the wheels to a negligible level at low rotation speed by a hydraulic power transmission mechanism such as a torque converter which is interposed in the transmission path.
However, the fluid transmitting mechanism is inevitably accompanied by deterioration in the transmission efficiency due to a difference between input and output rotational speed (slip).
Therefore, such a system is proposed in which, in place of the hydraulic transmission mechanism, a starting clutch is interposed in the transmission path described above, which may control the torque transmission capacity.
Such a transmission torque capacity control technique of the starting clutch is conventionally known and described in Patent Document 1, for example.
The transmission torque capacity control technique of the starting clutch in this document discloses that; (a) in a vehicle stopping state, the transmission torque capacity (engaging force) of the starting clutch is controlled in a manner in which creep torque can be transmitted (creep torque control), and (b) when starting from the vehicle stopping state, i.e., in a predetermined low vehicle speed range (when a torque converter is interposed, in a state in which the torque converter should be released from a lock-up state to disconnect input and output elements so as not to be connected directly) during a period in which the starting clutch is completely engaged from a released state, the transmission torque capacity (engaging force) is controlled such that the engine speed trajectory or path representing change of the engine rotational speed over time will assume a desired rotational trajectory that does not cause the start shock and starting delay (engine rotation trajectory control).
Incidentally, when performing the engine rotation trajectory control described in (b), the transmission torque capacity command value Tc of the starting clutch is calculated by the following equation.Tc=C×(Ne−Neoff)2  (1)Whereby,C: torque capacity coefficient of the starting clutchNe: engine rotation speedNeoff: engine rotation correction amountThus, by performing the engagement control of the starting clutch in order for the transmission torque capacity to attain the command value Tc described above, the engine rotation trajectory will be controlled as desired.
Patent Document 1: JP 2006-038057 A